Short answer is to get a Lee factory crimp die in the proper caliber. They are set up to give the proper crimp for the proper cartridge.

A quick and dirty way to determine crimp is to try to chamber a round base fist. If it goes in, taper, it it doesn't, roll. For example, disassemble your .45acp and remove the barrel. See how the round goes into the chamber base first? Hear the sharp "click/cloop"? That means, essentially, it headspaces on the case mouth. Now try to put a .38 into the chamber of a revolver base first. It won't go because of the rim. That means it headspaces on the rim. It isn't 100%, but it works more often that not.